Image: Wittenberg c. 1530 from the host's personal collection.
In May 1536 several prominent Reformed reformers traveled to Wittenberg to confess their understanding of what is received in the sacrament of Holy Communion and who receives it. Luther, Melancthon, and other Lutheran reformers readily signed on in agreement concerning this contentious doctrine. This was seen as a significant breakthrough and a celebrated establishment of fellowship and would later directly influence the Formula of Concord.
Read more about this topic here in Gordon Jensen's book.